A new type of X-ray camera has been developed which has the potential capability of simultaneously measuring in real time the dose and density spatial profiles of irradiated body elements in a patient undergoing radiation therapy. The camera is positioned in a non-invasive position on the patients side and detects photons scattered from the patients body. The camera system consists of a compact chamber with a slot aperture at the camera entrance plane, and an array of 100 X-ray detectors at the camera image plane. Each detector measures the X-ray signal emitted from a corresponding volume element that is irradiated in the patients body. Accordingly, the signals measured by the 100 detectors can provide information about the spatial distribution of the dose and density in the irradiated volume elements of the patients body. The goal of this proposal is to demonstrate that with proper calibration of the detector array, the camera system can function as an on-line, non- invasive, real-time measuring system of the dose and density distribution in irradiated body elements. The calibration would be carried out with different sizes of water phantoms and with selected X-ray, gamma-ray, high energy electron, or high-energy proton therapy beams.